## Trace File Location

Gap4 does not store the trace data within the gap4 database. Instead it stores the filename of the trace file. Usually the trace files are kept within the same directory as the gap4 database. If this is not the case gap4 needs to know where they are.

To make sure that gap4 can still display the traces we need to specify any alternative locations where traces may be found. The "Trace File Location" command (which is available from the gap4 Options menu) performs this task. It brings up a dialogue asking for the directory names. If there is just one directory to specify, its name should be typed in. If there are several directories to search through, they must all be typed in, separated by the colon character (":"). To include a directory name that contains a colon, use a double colon.

For example, on windows to specify two directories, use (eg) "`F::\tfiles1:G::\tfiles2`".

In addition to specifying directories, RAWDATA may also be used to indicate that the trace files are contained within a tar file. The syntax for RAWDATA is then `TAR=`filename. This can be combined with directories if desired (for example, `.:/traces/online:TAR=/traces/archive.tar`). In order to speed up accessing of traces within the tar file a command line utility named `index_tar` may be used. This produces a text index containing the filenames held within the tar and their offsets within it. Programs will then use this index file to provide a fast way of accessing the trace. The syntax for `index_tar` is: `index_tar` tar_filename `>` tar_filename`.index`. (For example "```index_tar traces.tar > traces.tar.index```".)

If the gap4 database has been opened with write-access this directory location will be stored as a database `RAWD` note (see section Special Note Types), which is read by gap4 when it opens the database. The demonstration data supplied with the package includes an example database (named DEMO.0) that has a RAWD note to specify that traces are fetched from a tar file within the same directory.

An alternative way of specifying the trace file location is by setting the `RAWDATA` environment variable. On Unix and Windows NT this is straightforward (although system and shell specific). However on Windows 95 this may prove difficult (and at least require a reboot), so manually setting the environment variable is no longer recommended.